Chemical structure and antioxidant activity of the essential oil isolated from <i>Phlomis olivieri</i> benth. (lamiaceae)

<i>Phlomis olivieri</i> Benth. is an aromatic endemic species in Iran belongs to family Lamiaceae. In this research, the essential oil of this medicinal plant was isolated and its antioxidant activity investigated in four populations including Hamedan, Kermanshah, Kurdistan, and Lorestan. For this, aerial parts of the plant were collected, dried in shadow, and milled. The essential oil was isolated by Clevenger apparatus and then analysed GC-MS. Antioxidant activity of essential oil evaluated by its activity in scavenging stable DPPH radical. The results indicated availability of 17 constituents in the essential oil structure while caryophyllene being dominant of them (peak 4, retention time: 9.585 min, 24.093% on total). Regarding the antioxidant effects, ANOVA was significant (F_{3, 8}= 50.42). Accordingly, the highest and lowest activities were observed in Hamedan and Kurdistan populations (159.17 ± 10.50 µg/ml vs. 69.45 ± 3.24 µg/ml), respectively. Therefore, this valuable medicinal plant has suitable constituents with high antioxidant activity which can be considered in different aspects.